Drill bit



June 22, 1954 l B, A, MACKEY 2,681,573

' DRILL BIT Filed oct. 11. lgs:

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Patented `lune 22, 1954 UNITED` STATES PATENT OFFICEv DRILL BIT Bruce A. Mackey. Libertyviue, 111. Application October 11, 1952,` Serial No. 314,298

`3 Claims. (Cl. 145-116) My invention relates to improvements in drill bit construction.

My invention relates more particularly to drill bits of the type used for boring large holes in wood, plastics, aluminum or other generally similar materials and contemplates the provision of a drill shank having a bit blade holder capable of operatively receiving any one of a plurality of different size bit blades which are easily and quickly attached or removed.

My invention further contemplates the provision of extensions for the shank so that holes in ceilings or other places comparatively remote can easily be made by the employment of one or more of the extensions depending upon the distance from the portable electric motor to the location of the proposed openings.

Other features of the invention and the improved construction disclosed include the provision of a drill bit or blade having a thin curved cutting edge which gives a positive lead rake This provides quicker and easier boring of holes than can be obtained with straight edge blades of the type at present on the market.

Other objects and advantages will be more apparent from the following description wherein reference is made to the accompanying drawing upon which:

Fig. 1 is a side elevational view of a portable electric drill motor having a chuck in which the improved bit holder shank and bit of my improved invention is shown;

Fig. 2 is a side elevational view showing the manner in which the assembly is employed for boring holes in ceilings or other inaccessible places, the bit holder shank being connected to the chuck of the motor by a plurality of shank extensions;

Fig. 3 is a side elevational view of the bit holder shank and bit;

Fig. 4 is a fragmentary cross sectional view through the bit holder shank and one of the shank extensions taken generally on the line l-l of Fig. 2;

Fig. 5 is a side elevational view of one of the bit blades;

Fig. 6 is a plan view thereof;

Fig. '1 is a bottom view thereof; and

Fig. 8 is a side view of the same.

In the embodiment of the invention which I have chosen to illustrate and describe the same in Fig. 1, I have shown a portable electric drill motor I 0 of the usual type having a tool receiving chuck I2 extending forward from the same.

I provide a bit holder shank I4 capable of being securely fastened in the chuck in the usual manner at one end. The other end of the bit holder shank has an enlarged elongated shoulder I6 which is a holder for a drill bit or blade I8. The holder has a slot 20 extending inwardly from the end of the same and is further provided with a set screw 22 screw-threadedly mounted therein and adapted to engage the opening 24 inthe bit blade I8 to securely fasten the blade to the end of theholder IG.

The bit blade I8 is preferably furnished in a plurality of sizes for drilling holes of a plurality of sizes. For example, a set may consist of l, 5/8", 3A", '7/8 and 1" bit blades so that holes of these sizes may be drilled with the set provided.

Each of the bit blades I 8 is generally rectangular in shape as shown having a leading point 25 at its forward end, parallel side walls 28 and 30 and a back wall 32 having a square slot 34 therein. Each blade has a portion of the side walls '28 and 30 bent from the plane of the body in the direction of rotation. The lower edge 33 of each of the bent portions is sharpened to provide cutting edges and the edges of the side wall portions 29 and 3I are cleared by sharpening the edges at a slight angle provide a rake cutting angle so that shavings will be fed inwardly from the edge of the hole being bored and a much cleaner and smoother bore is obtained. In addition, by the use of the angled forward cutting edges 33 much more rapid progress is made and holes are much more quickly bored and will be cleaner and smoother on their interior walls when finished. By presenting the angled edge, a shearing action is effected, as contrasted with a scraping action where the cutting action is in the plane of the blade.

When it is desired to bore holes in inaccessible places such as in the ceiling or in places that cannot be reached with the ordinary =bit holder shank I4, I employ a plurality of shank extensions 4U. One end of the extension 40 may be fastened in the chuck I2 of the portable motor I0 and the other end fastened by means of a set screw 42 to a fiattened shoulder 44 on the opposite end of an adjacent extension 40. The shoulder is adapted to fit into an opening 46 in the end of the extension 40 there also being a bore 48 to receive a round reduced shoulder 5U on the end of an adjacent extension 40.

With this construction it can be seen that within reason boring of holes may be done a conslderable distance from the operator by the use of the extension shanks which I have provided.

attached or removed from the bit holder it can Y be seen that when a blade becomes dull or is broken it can be easily removed and replaced.

Further, by reason of making the bits or blades detachable from the bit holder when breakage does occur it is considerably less expensive than when it occurs in the use Vof drill bits that are an integral part of the bit holders.

I contemplate that changesand modificationsv may be made in the exact details shown andI 4 portion of each of said side edges beingbent from the plane of the body of the blade in the direction of rotation, each of said front cutting edges being in a continuous line from the base of said lead point to the side edges of said blade, said portions of said side edges of the blade being cleared to provide side cutting edges.

3. A flat drill blade generally rectangular in shape, having front cutting edges, a back edge and side edges, a centrally located tapered lead point extending forward from the front edges of the same, means at its back edge for attachment to a holder, the front cutting edges and a portion of each of said side edges being bent from the plane of the body of the blade in the l direction of rotation, each of said front cutting edges being in a continuous line from the base do not Wish to be limited in any particular; rather what I desire to secure and protect by Letters Patent of the United States is:

1. A flat drill blade generally rectangular in shape, having front cutting edges, a back edge and side edges, a centrally located tapered lead point extending forward from the front edges of the same, means at its back edge for attach'- ment 4to a holder, the front cutting edges and a portion of each of said side edges being bent from the plane of the body of the blade in the vdirection of rotation, each of said front cutting edges being in a continuous line from the base vof said lead point to the side edges of said blade.

2. A at drill blade generally rectangular in shape, having front cutting edges, a back edge and side edges, a centrally located tapered lead point extending forward from the iront edges of the same, means at its back edge for attachment to a holder, the front cutting edges and a of said lead point to the side edges of said blade.'

said front cutting edges being angularly disposed forward from the plane vof the body of said blade to eiect a shearing action during a boring operation.

References Cited in the file of this patent UNITED STATES PATENTS v Number Name Date 124,089 Shepardson Feb. 27, 1872 238,002 Ransom` Feb. 22, 1881 315,079 Shotts Apr. 7, 1885 1,056,610 Watkins Mar. 18, 1913 2,291,729 YKoett Aug. 4, 1942 2,543,206 Smith Feb. 27, 1951 FOREIGN PATENTS Number xCountry Date 814,939 Germany Aug. 2, 1951 

